Integrating photometer



June 9, 1942. H LAMB 2,286,036

INTEGRATING PHOTOMETER Filed Jan. 10, 1940 reversing device of theapparatus. "to provide integrating apparatus of ratented June 9, 1942INTEGRATING PHOTOMETER I Anthony H. Lamb,

Elizabeth, N. J., asslgnor to Weston Electrical Instrument Corporation,

Newark, N. J., a corporation of New Jersey Application January 10, 1940,Serial No. 313,285

13 Claims.

This invention relates to integrating apparatus and more particularly toapparatus of high sensitivity for integrating against time a variablefunction that may be measured by an electrical measuring instrumenthaving a sensitivity of the order of a milliammeter or microammeter.

The copending application of Roswell Ward Gilbert, Serial No. 284,805,filed July 15, 1939, now Patent No. 2,239,363, granted April 22, 1941,describes and claims light integrating apparatus including a pivotedcoil that oscillates in a magnetic field and, in its alternate endpositions, closes relay contacts for the actuation of a counter and of apolarity reversing switch in the leads to the coil. The coil is mountedin jewel bearings and has an angular velocity that varies with themagnitude of the current flowing in the coil, the total travel or numberof oscillations of the coil in a given time thus being a measure of theintegrated values of the variable function corresponding to the currentflow through the coil.

An object of this invention is to provide inte grating apparatus of thesensitive oscillating coil type that includes simple and efficientcircuits for controlling the indicating and polarity An object is thesensitive oscillating coil type that includes a solenoid actuatedratchet device for operating both the polarity reversing switch and thecounter, and a relay controlled by the coil displacement to energize theratchet solenoid. A further object is to provide apparatus of the typelast stated in which the relay is of the vacuum tube type. A furtherobject is to provide integrating apparatus including an oscillating coilthat displaces a contact arm between a pair of contacts, a polarityreversing network including a single pole switch connecting the coil toa current source, a ratchet mechanism for actuating the switch, and arelay controlled by the contact arm nism. Another object is to provideintegrating apparatus including an oscillating coil controlling relaycontacts, a circuit energized by said contacts for actuating a ratchetmechanism, and a counter and polarity reversing switch both actuated bythe ratchet mechanism. A further object is to provide integratingapparatus of the type last stated in which the counter includes anarcuate scale graduated in values 01' the integrated quantity, a pivotedpointer movable over the scale and frictionally coupled to a shaft thatand contacts for advancing the ratchet mechais driven by the ratchetmechanism, and a signal or control circuit including a switch operatedby the pointer when it reaches a predetermined position along thegraduated scale.

These and other objects and advantages of the invention will be apparentfrom the following specification when taken with the accompanyingdrawing in which:

Figs. 1, 2 and 3 are circuit diagrams of light integrating apparatusembodying the invention.

The invention may be employed for integrating other quantities againsttime but will be described with respect to the integration of lightvalues as represented by the current output of a photocell of thebarrier layer or current-generating type. The current output of such acell is a substantially linear function of the illumination at the.cell, but the generated current is of such a minute order that onlyinstruments of high sensitivity can be operated out of acurrent-generating photocell. Phototubes can be worked into vacuum tubeamplifiers to develop appreciable power for actuating integratingmechanisms but the vacuum tube phototube is not sufiiciently stable toinsure a reasonable degree of accuracy in operation. The accurateintegration of fluctuating illumination values has presented anexceedingly difiicult design problem and it is to be understood that theinvention may be employed for the integration of factors capable ofdeveloping electrical voltages or currents of small absolute values butof an order substantially higher than the currents developed by acurrent generating photocell.

In Fig. 1 of the drawing, the reference numeral l identifies a barrierlayer type photocell that is connected through a polarity reversingswitch 2 of the conventional double pole, double throw type to a coil 3that is pivotally mounted in jewel bearings, not shown, for oscillationin the field of a permanent magnet 4. As described in the Gilbertapplication, the leads to the coil 3 are highly flexible and imposesubstantially no torque load on the moving system. The coil 3 and magnet4 resemble a sensitive microammeter but differ from such an instrumentin that no torque springs are provided .and the coil 3 is displacedfreely in the magnet field at a speed that depends upon the current flowthrough the coil.

The pivoted coil 3 carries a contact arm 5 and displaces the samebetween spaced contacts 6 that also serve as stops to limit theoscillatory movement of the coil in opposite directions. The contact arm5 is connected by a lead 1 to the cathode, shield grid and one heaterterminal of a hot-cathode gas electrode 8 such as those sold by RadioCorporation trolled rectifier service types 2050 and 2051. The

of arnerica for grid-consistors l0, it that may s a m designationscontacts are Joined. and connected bya lead-8 to the junctionof rebe: ofthe order of 1.5

megohms and serially connected between the in ner or control grid andthe other heater terminal."

The plate circuit of tube 8 includes, in parallel,

- of the separate, counterv by} an iindicator tothe ratchet mechanismshaft. 3 The circuit net;

the solenoid l2 of a counter i8 and the solenoid ll of a ratchetmechanism comprising the armature l5 and cam l8 on a shaft II thatcarries a cam 18 for shifting the actuating bar l8 of the polarityreversing switch 2. The circuits of tube 8 may be energized in the usualmanner from an alternating current source such as a customary 110 volt,60 cycle power and light circuit through a transformer 20 having atapped secondary including a winding 2| connected-between the plate.

' shown' in Fig.3, the full photocellgcurrent flows 25 and then div-idesto flow,

and cathode of tube 8 and a winding 22 for sup plying current to theheater circuit. The sense of the windings 2 I, 22 and the connections tothe heater circuit are such that the control grid is tacts 8, and thetube then passes plate current,

on half cycles when the plate potential is positive, to energize thesolenoid l2 of the counter and the solenoid ll of the ratchet mechanism.Shaft ll of the ratchet mechanism is thereby advanced one step to movecam l8 and plunger is to actuate the polarity reversing switch 2. Thecoil 8 then travels in the opposite direction until the contact arm 5engages the other contact 8 to supply another current pulse to thesolenoids l2 and H. The coil thus continues to oscillate so long ascurrent is supplied by the photocell Lof. operation is therefore as thatdescribediabove' "Fig.1 apparatus.

alumnus f- Further simplifications oi -the. eiectricaland I mechanicalelements 'of the apparatus may be a-change intheithereplace'ment. r

effected. as shown in Fig.8, by; polarity reversing network" andworkconnecting the eludes the resistors single throw switch being connectedbetween the switchx30. when the'switch 20 is open, as

through the resistor I a in parallel, through resistor and the coil 8 inseries with the resistor 28. A closure of switch 80 througha one-stepmovement of cam l8 by 1 the ratchet mechanism connects the resistor 28across the photocellgfin :parallel"withv a path that includes theresistor 25 andcoil 8 in parallel with 25' each other and inseries-withthe resistor "28.

and the total travel of the. coil is a 'measure of V the integratedlight'values. The apparatus may be designed to read directly in anydesired units, for example foot-candle-seconds. by proper selection ofthe moving coil constants, and adjustment of the spacing of contacts 8to determine the angle of oscillation of the coil in accordance with thesensitivity of the photocell.

The integrating apparatus of Fig. 2 differs from the describedconstruction only as to the polarity reversing system, and thoseelements of the Fig. 2 apparatus that are identical with those of theFig. l circuit are identified by the same reference numerals but willnot be described in detail. A pair oi. resistors 24, 25, preferably ofthe same magnitude, are connected in series between the leads from thephotocell and the coil then the other resistor as the switch blade 28' Iis moved from one contact to the other by the plunger is and cam l8 ofthe ratchet mechanism.

Inspection of this network will show that the direction of current flowthrough the coil 8 is re-, the actuation of the switch blade 26- versedby at each energization of the ratchet mechanism solenoid H by anengagement of the arm 5 with one of the contacts 8.

coil contact The method The direction of current flow through coil 18 isthusrevcrsed by the closing of the switch 20;

' The optimum values of the resistors 24, 2 5.

and 28 will vary with the measuring range, the characteristics of theintegrating instrument and the photocell sensitivity, but there, may bewide latitude in the selection of the resistance values withoutmaterially altering theefllciency or accuracy of the apparatus. The'following data is indicative of values that are satisfactory but it isto be understood that the invention is not limited to any particularresistance values or ranges of values. Resistors 24, 25 may each be 100ohm resistances and resistor 28 maybe a 99 ohm resistance when coil 8has a resistance of v1 ohm and the photocell i has a resistance of theorder of 3000 ohms. The currents flowing in the parallel paths are equalwhen the switch 88 is open, and-therefore exactly. one-half of the totalphotocell current flows through the coil 8 of the integratinginstrument. The current flow is not equally divided in the parallelpaths upon closure of switch 30, and the current through coil 3 isapproximately 2% below that which takes place when switch 30 is open.The angular velocity of the coil 3 for a given light intensity or totalphotocell current thus varies slightly with the direction of travel ofthe coil 8 but this variation does not affect the accuracy cf theapparatus as it will be calibrated over a period of time foran averagespeed that, for the stated resistance values, will be slightly above theactual coil speed in one direction and slightly below the coil speed inthe opposite direction.

The indicator of the Fig. 3 apparatus comprises a gear 3| on the ratchetmechanism shaft I1 and meshing with reduction gearing 82 to drive ashaft 33 carrying a pointer thatis movable over ,an arcuate scale 35graduated in units of integrated light-time values. The hub 26 of thepointer 34 is frictionally coupled to theshaft 38 to permit a manualsetting of the pointer 84 to a desired value. The-ratchetmechterclockwise to return the pointer 30 to zero position whentheintegrated light value at the photocell i reaches the selected value.

A switch I! may be positioned for actuation by the pointer 34, when itreaches-zero posiwm: swears; I

anism rotates the shaft 38 and pointer 84 coun- 2,sao,ose

tion, to actuate a signal or control circuit. As shown in Fig. 3, theswitch I! is a single-pole double throw switch that is normally closedon one contact to energize a signal lamp it from a secondary winding 39of the transformer 20, and is actuated to its alternative position bypointer 34 to close a circuit through a signal device 40 that may be alamp, a bell or the like.

Each of the described embodiments of the invention is highly stable whenoperated from the usual power lines that are subject to some voltagefluctuation and the marked reduction in the number of relay elements andswitches, as compared with the electromagnet relay circuits of theGilbert application, results in reduced initial and maintenance costs.There is latitude in the design of the grid-controlled relay tubes andin the tube circuits, and it is to be understood that variousmodifications that may occur to those familiar with the art fall withinthe spirit of my invention as set forth in the following claims.

I claim:

1. In an integrating photometer, the combination with an integratingsystem comprising means establishing a magnetic field, a coil mountedfor free oscillation in the magnetic field, a contact arm carried bysaid coil, and relatively fixed contacts spaced from each other alongthe path of said contact and electrically connected to eachother, of aphotoelectric cell of the current-generating type, circuit elementsincluding a polarity reversing switch connecting said photocell to saidcoil, means including a solenoid for actuating said polarity reversingswitch, a vacuum tube having said solenoid in the output circuitthereof, and a circuit including said contact arm and contacts forcontrolling conduction through-said tube.

2. In an integrating apparatus, the invention as claimed in claim 1,wherein said means for actuating said polarity reversing switch includesa ratchet mechanism operated by said solenoid.

3. In an integrating apparatus, the invention as claimed in claim 1,wherein said means for actuating said polarity reversing switch includesa ratchet mechanism operated by said solenoid, in combination with meansactuated by said ratchet mechanism for registering the oscillations ofsaid coil.

4. In integrating apparatus, means establishing a magnetic field, a coilmounted for oscillation in the magnetic field, circuit elements forsupplying to said coil a current that varies in magnitude with a factorto be integrated, said circuit elements including a switch forreversingthe polarity of the current suppliedto said coil, a relay circuitincluding relatively fixed contacts and a contact arm carried by saidcoil, means for actuating said polarity reversing switch. means forregistering the oscillations of said coil. and ratchet mechanismenergized by said relay circuit for operating both of said means.

5. Integrating apparatus of the type including an oscillating coilconnected to a variable direct current source through a polarityreversing switch. characterised by the fact that a pair of resistors areserially connected across saidcurrentsource,saldswitchisofthesinglepoletypeandsaidcoilisconnectedbetweentheiunctionof saidresistorsandacontactofthsswitch.

' tween a pair of spaced contacts connected to opposite terminals ofsaid current source, and said .coil is connected to the movable switchcontact.

7. Integrating apparatus as claimed in claim 5, wherein said switchcontact is connected through a resistor to one terminal of said currentsource, and the cooperating switch contact is connected to the otherterminal of said current source.

8. In integrating apparatus, a current generating photocell, means forestablishing a magnetic field, a coil pivotally mounted for oscillationin said magnetic field, circuit elements including a. polarity reversingswitch connecting said coil to said photocell, relay contacts includinga contact arm carried by said coil and spaced relatively fixed contacts,a solenoid-operated ratchet mechanism for actuating said polarityreversing switch, and a relay circuit including said contact arm andcontacts for energizing said ratchet mechanism.

9. In integrating apparatus, the invention as claimed in claim 8, incombination with means energized by said relay circuit for registeringthe oscillations of said coil.

10. In integrating apparatus, the invention as claimed in claim 8, incombination with means actuated by said ratchet mechanism forregistering the oscillations of said coil.

11. In integrating apparatus, the combination with means establishing amagnetic field, a coil mounted for oscillation in the magnetic field, acurrent source connected across said coil for supplying thereto acurrent that varies with a factor to be integrated, and means forreversing the direction of current fiow through said coil to efiectoscillation thereof in repeated cycles of movement of predeterminedextent, of means for registering the number of oscillations of saidcoil; said registering means including a relay circuit having contactsclosed by said coil at its end positions, a shaft and means energized bysaid relay circuit for imparting a step-by-step rotation to said shaft,a pointer carried by said shaft, and a graduated scale cooperating withsaid pointer.

12. In integrating apparatus, the invention as set forth in claim 11,wherein said pointer is frictionally connected to said shaft, and saidmeans energized by said relay circuit displaces said pointer towards thezero graduation of said scale. whereby said pointer may be manually setat a desired value on said graduated scale and then returned to zeroposition upon a time integration of the factor to the desired value atwhich the pointer was manually set.

13. In integrating apparatus, the invention as set forth in claim 11,wherein said pointer is frictionally connected to said shaft, and saidmeans energized by said relay circuit displaces said pointer towards thezero graduation of said scale, whereby said pointer may be manually setat a desired value on said graduated scale and then returned to zeroposition upon a time integration of the factor to the desired value atwhich the pointer was manually set, in combination with a circuitincluding a switch having a movable contact positioned for actuation bysaid pointer upon arrival at zero position on said scale.

ANTHONY H. LAMB.

